The present invention relates to a process and apparatus for the selective electroplating of electrical contact elements, which process is used for coating at least one contact surface of a metal base for the contact elements with an electrolyte containing a material with higher conductivity as compared to the base (see the report of the 2.sup.nd EAST Congress, November 1991, publisher: Eugen G. Leuze, Saulgau, 1992, pages 30 to 37).
Such a process is used, for example, for the coating of contact protuberances of electrical contact elements. The process is used mainly for the gold-plating of contact protuberances for spring contacts composed of copper-containing materials. Basically, it can also be used for bases composed of other materials, e.g. bronze, nickel silver, copper-beryllium or stainless steel. In each case, one contact surface of a base composed of an electrically less, highly conductive metal is coated with an electrically highly conductive metal. Metals suitable for this are preferably gold and palladium, but also platinum, ruthenium, rhodium, silver, nickel or copper can also be used. Basically, it is generally sufficient in this case if only the direct contact region of a contact element is coated with the highly conductive material. Since for economic reasons the given problems are most serious for "gold", what is hereinafter explained is the electroplating with gold of contact springs made of bronze, and is representative for all other possible materials.
Based on the known process according to the above-mentioned magazine "EAST" Report, contact springs that are punched out of an endless band and connected therein are electroplated while passing through. During this process, the section of the contact springs to be coated is brought into contact with a cylinder, which rotates around its axis and is wetted on the surface with electrolyte. With this process, it is unavoidable that the ends of the contact springs are coated completely. In addition, the use of coating material is relatively high. The process is therefore not economical, in particular if gold is used as coating material.
It is, therefore, the object of the invention to provide a process and apparatus of the above type in which less gold is used.